This chapter describes the indices of stress response most frequently examined in children, and reviews known developmental correlates of these stress reactivity measures as well as important methodological considerations. It focuses on the noninvasive and relatively inexpensive indices of stress response that are most commonly used in developmental and epidemiological field research. The chapter examines existing research pitfalls, identifies new work occupying the advancing edge of this field and suggests potential future directions. As stress reactivity is a dynamic process, evolving with neurobiological maturation and environmental exposures, it is important to examine whether and how associations between stress reactivity and adaptive functioning change across different developmental periods within the same individuals. Future research need to employ more advanced, longitudinal analytical procedures when examining the role of stress reactivity in development. To date, most studies of stress reactivity have relied on simple bivariate correlations, analyses of variance, and regression analyses.